text: describe('flatten array', function () {
    it('should flatten an array', function () {
      var arr = [1, 2, [1, 2, [3, 4, 5, [1]]], 2, [2]],
         expected = [1, 1, 1, 2, 2, 2, 2, 3, 4, 5];
         arr = arr.flat(3).sort();
      expect(arr).toEqual(expected);
    });
  });
  